A tunable laser is a laser whose output wavelength can be varied in a controlled fashion. For example, changing the cavity length by moving a mirror at one end of the cavity or by heating the cavity itself may change the wavelength. But a typical tunable laser is fundamentally limited in wavelength tuning range by the bandwidth of its gain media. And the tuning speed is limited by the mechanical speed of the moving mirror or the speed with which the cavity heats up or cools down. In addition, a tunable laser with a free-space tuning element, such as a moving mirror, exhibits worse shock and vibration performance and reliability than other lasers.